Description
Students explore why plants and animals may need support systems and discover that plants are the main source of energy in the food chain. Both of these concepts may then be applied to understanding how life may form on other planets.

Objectives
Students will:
• Compare and contrast the behavior of a water-filled plastic bag, both outside and inside of a container of water.
• Understand the differences between environments with gravity and environments with reduced gravity.
• Design and build an exoskeleton or an endoskeleton for an animal of their own invention.
• Identify plants as the main source of energy in the food chain.

Weighty Questions, pages 1–4
Muscles and Bones: Activities Guide for Teachers, National Space Biomedical Research Institute
In this activity, the students will compare and contrast the behavior of a water-filled plastic bag, both outside and inside a container of water.Keywords: muscles and bones

Supporting Structures, pages 5–7
Muscles and Bones: Activities Guide for Teachers, National Space Biomedical Research Institute
In this activity, the students build upon the knowledge gained from the first activity to create an internal or external skeleton designed to support an animal of their invention.Keywords: skeleton

Chain Games, pages 47–50
The Case of Zany Animal Antics: 2004–2005 NASA SCI Files™ Series
Students explore the operation of a basic food chain from the sun, to plants, to animals. To understand the complexity of life and where it may exist, the food chain should be examined. The teacher should relate the skeletal structure to protection.Keywords: complexity of life, food chain